Drug abuse and HIV are epidemics, which provide unique challenges in the pregnant population. Given the use of drugs of abuse and HIV therapies in pregnant women, it is important to characterize the pharmacokinetics (PK) and distribution of these drugs in this population. The long tern goal of this project is to define how the gestation period affects the placental and blood-brain transport and maternal PK of drugs and subsequent fetal exposure. Specifically, we are interested in evaluating drugs which are substrates of P-glycoprotein (P-gp) including drugs of abuse and therapeutics, and HIV protease inhibitors (Pis). Additionally, we intend to evaluate the impact of co-administration of drugs of abuse or therapeutics and HIV-Pls. Our hypotheses are: 1) the activity of P-gp in the brain is variable throughout pregnancy as has been reported for the placenta; 2) these alterations in transporter activity will affect the amount of drug distributed to the fetus and brain at different gestational periods; and 3) co-administration of HIV protease inhibitors and drugs of abuse will result in altered fetal and brain distribution. In order to test these hypotheses the following specific aims will be pursued: Specific Aim 1: Determine genetic expression for transporters in the placenta and brain at various gestational times using a gravid mouse model. Briefly, RNA and protein membranes will be extracted from placental and brain tissue collected at various gestational periods. RNA will be analyzed to determine the expression of numerous genes using microarray analysis. The expression and activity of P-gp will be determined from RNA samples using RT-PCR and from protein samples using Western Blot analysis; Specific Aim 2: Characterize the maternal PK and maternal- fetal and maternal blood-brain transport of P-gp substrates at various gestational times using a gravid mouse model. Ritonovir and saquinavir (HIV-Pls) and methadone, cocaine, and heroin will be evaluated; Specific Aim 3: Examine the influence of potential drug-drug interactions on maternal PK and maternal-fetal and maternal blood-brain transport following co-administration of P-gp substrates at various gestational times using a gravid mouse model. Ritonovir will be evaluated with methadone, cocaine, or heroin. For aims 2 and 3, mice will be dosed with test agent(s) and blood and fetal and brain tissue collected and analyzed for drug concentration. Maternal PK parameters and fetal and brain partition coefficients will be compared. This project is designed to increase our knowledge of how gestation age affects the transfer of drugs to the mother's brain and fetus; specifically drugs of abuse and therapies and HIV therapies. This knowledge may aid in an assessment of these drugs in pregnant women and their subsequent clinical risk and/or benefit. [unreadable] [unreadable] [unreadable]